delphi 桌面文字

var
     hDesktop : THandle ;
    s : string ;
function EnumChidProc(h:THandle;lp:DWORD):bool ; stdcall ;
    var
    cBuf : array[0..255] of char ;
begin
    GetClassName(h,cBuf,255) ;
    if StrComp(cBuf,'SysListView32')=0 then
    begin
    hDesktop:=h ;
    Result:=false ;
    exit ;
    end ;   

Result:=true ;
end ;

procedure TForm1.Button1Click(Sender: TObject);
var
     h : THandle ;
    dc : HDC ;
    DesktopCanvas:TCanvas;
     x,y ,z:integer;

begin
    x:=strtoint(edit2.text);
    y:=strtoint(edit3.text);
    z:=trackbar1.Position;
    h:=FindWindow('Progman',nil) ;
   EnumChildWindows(h,@EnumChidProc,0) ;
    Caption:='句柄：'+inttohex(hDesktop,8) ;
    dc:=GetDC(hDesktop) ;

    s:=edit1.Text ;
    DesktopCanvas := TCanvas.Create;
    DesktopCanvas.Handle := DC;
    DesktopCanvas.Font.Color := clRed;
    DesktopCanvas.Font.Name := 'Arial Black';
    DesktopCanvas.Font.Size := z;
    DesktopCanvas.Brush.Style := bsClear;  

    DesktopCanvas.Textout(x, y, s);
    DesktopCanvas.Free;
  
   // Windows.TextOut(dc,x,y,pchar(s),length(s)) ; ///
// ReleaseDC(hDesktop,dc) ;   ///

end;